Fuel cells are increasingly being used as power sources for electric vehicles and other applications. An exemplary fuel cell has a membrane electrode assembly (MEA) with catalytic electrodes and a proton exchange membrane formed between the electrodes. During operation of the fuel cell, water is generated at the cathode electrode based on electrode chemical reactions between hydrogen and oxygen occurring within the MEA. Efficient operation of a fuel cell depends on the ability to provide effective water management in the system.
Gas diffusion media plays an important role in PEM fuel cells. In general, diffusion media needs to wick product water away from the cathode catalyst layer while maintaining reactant gas flow from the gas flow channels through to the catalyst layer. In addition, the proton exchange membrane between the electrodes works best when it is fully hydrated. Accordingly, one of the most important functions of the gas diffusion media is to provide water management during fuel cell operation.
For best water management, it is desirable to provide a gas diffusion medium having a desirable balance of hydrophilic and hydrophobic properties. By providing gas diffusion media with a proper balance of hydrophilic and hydrophobic properties, it is possible to prevent flooding in the cell due to excessive accumulation of water in the gas pores while maintaining proper hydration of the proton exchange membrane.
Accordingly, it would be desirable to provide gas diffusion media having improved balance of hydrophobic and hydrophilic properties that could be exploited to provide efficient water management in fuel cells.